Year	Percent
1977	13.78756
1978	15.93698
1979	11.82696
1980	18.95609
1981	22.36588
1982	23.74114
1983	28.62628
1984	32.82728
1985	38.67861
1986	42.26363
1987	22.93064
1988	32.09813
1989	36.48457
1990	28.58715
1991	22.12471
1992	21.78628
1993	17.55182
1994	16.55582
1995	16.04569
1996	14.5968
1997	12.40735
1998	13.01397
1999	12.89249
2000	9.82128
2001	11.3348
2002	12.12915
2003	13.00034
2004	8.01865
2005	7.10879
2006	6.33357
2007	6.06056
2008	5.68989
2009	6.50275
2010	6.13633
2011	7.81577
2012	6.53305
2013	7.55933
2014	12.52998
2015	9.98299
2016	18.93874